Since the 21st century, the industry of televisions has evolved rapidly towards flat panel, networking and intelligentize televisions, and the calculation capability, storage capability and display capability of the televisions have improved rapidly. For most of the integrated intelligent television products in the existing market, the user have to upgrade the entire television to achieve the upgrading of the function of the entire product, which may bring an extra expense and waste to the user.
In view of this, modular television products which may be functionally separated have emerged, and such products reserve fundamental functions of the unity machine of the television, and add corresponding external devices according to the demands of different users. In this solution, while some external device is operating in the foreground, a control instruction of another external device or the television host needs to be input in a control mode corresponding thereto. For example, a volume adjustment instruction for the television host or an audio device connected with the television host is input to a network set-top box operating in the foreground, to control the television host or the audio device to adjust the volume.